Drop-In LiFePO4 Batteries – Be an Educated Consumer

[Johann]

I use a Victron solar controller and BMV-712 BMS on my boat and have been looking at the Victron CerboGX to monitor my batteries and charging system while I'm away.. And while you can monitor and manipulate your connected systems remotely (e.g. turning off solar power), it doesn't appear there's any new functionality. So, for example, I cannot now tell my shore charging system to charge my batteries to 80% and stop. VRM doesn't change that for my existing system, but please set me straight if that's not the case.

If you want SOC based control you could use the relay from the BMV to send an allow/disallow charging signal based on SOC. If your chargers have a remote switch (Multis, some MPPTs) this would work without extra configuration. Otherwise you could use a charge bus with a solenoid controlled by the BMV relay. I prefer to just use voltage (for now) as there isn’t a need for a precise SOC IMHO. Just low, medium, or full is good enough for me.

Perhaps a LifePO BMS is much more functional, like my Tesla which (as has been pointed out) has an app which allows me to see the state of charge of my battery, start or stop charging manually, set a charging % limit, direct it to charge during low grid load periods, or even set a departure time so the car charges in time to be ready when I'm headed out the door. I've owned three electric cars since 2012, and this tech has been around since the first one I owned, a Nissan Leaf.

Totally agree it could be a lot easier. Instead of having to adjust each charger, a single app that would change all the charger settings at once would be very nice.

 

[njlarry]

Dont know much about batteries, old school flooded for me, but so good to see you back! Glad your doing better

 

[deminimis]

Great article and great thread. We've been running a 200AH SOK for the past year as our house batt. It has performed great. I may add a second. We were still using a LA batt as my outboard starter batt. Both systems are isolated form each other. Now I've pull the LA batt and I'm installing a small LiFePO4 powersports battery as my starter battery (well know company). It has a built-in BMS and it's sized for a 1100Waverunner, BMW touring motorcycles and so on, so it should not have any issue with my 327cc outboard. Weighs less than 3#. Battery max charging amps is 29 (if I recall correctly) and my little Suzuki's alternator puts out 12 amps tops (again, if I recall correctly). Creates a pretty good safety margin. What I find interesting is the batt mfr claims that the batt can be charged with a regular ol' LA battery charger. I guess that bodes well for having the alternator charge the batt while the outboard is running. I have proper LiFePO4 chargers as well (shore power only for the starter batt). Trying to decide, if I should mount the batt inside or out. I mean, I already have a 200AH batt inside (under solon seating) so why am I even concerned? I've been breaking in my new outboard (tank) and the batt has been as cool as the other side of the pillow the entire time (well, it's only been an hour). I think the risk is minimal, inside should be just fine, and I should just make sure I have an additional fire extinguisher mounted near it. At least that's my thinking today (and it may change tomorrow). I suppose if I was really being cautious, I could install a batt cut off switch and only use the batt for starting and tilt duties when the OB is not running (Suzuki, even with EFI, does not require a battery to operate) and charge the batt only with hooked up to shore power, but I do not think that is necessary. Dunno....

 

[shemandr]

From what I've read, a LiFePo4 battery, once on fire, is difficult or impossible to put out with a conventional fire extinguisher. My source is an article in Boating World written by Virginia Koetzner. Her article is largely based on a BoatUS report on Li batteries. She does cite sources on the pro Li side as well.
In the East Marion car crash that killed 4 people, it took the fire department 2 hours of spraying water on it to extinguish the fire. It was reported to be a head on collision at speed. So the battery didn't directly cause the accident. The fire was an after effect. But, there's a lot of energy in those batteries!

Lithium Batteries – Does the Good Outweigh the Bad? – Long Island Boating World

liboatingworld.com

 

[deminimis]

I just blasted through that article, skipping much as I have to run. However, it appears she does not distinguish between battery chemistries and the accidents she references. Perhaps it's in there and perhaps she references LiFePO4 specific incidents, but doing my best Evelyn Wood, I did not see it. I trust the FAA report better. I try and locate it when I get back.

 

[deminimis]

Well, I have a minute. 2017 study: https://www.fire.tc.faa.gov/pdf/TC-16-17.pdf

In a nutshell:
"In general, of all of the lithium-ion cells that were tested, LiFePO4 would be considered the
safest cathode material because of the relatively low temperature rise and the resulting low
likelihood for thermal runaway to propagate. LiCoO2 and LiMnNi would be considered the most
hazardous because of the relatively large temperature rise and high probability for propagation of
thermal runaway to adjacent battery cells. "

Still, it does gimme the heebie-jeebies.

 

[deminimis]

Aircraft Spruce is now selling LiFePO4 batts. They have a very bold disclaimer that these are not FAA approved and intended for experimental aircraft only. However, if folks are sticking LiFePO4 in planes (experimental or otherwise), that is encouraging. Okay, I really have to run!!

 

[dlochner]

From what I've read, a LiFePo4 battery, once on fire, is difficult or impossible to put out with a conventional fire extinguisher. My source is an article in Boating World written by Virginia Koetzner. Her article is largely based on a BoatUS report on Li batteries. She does cite sources on the pro Li side as well.
In the East Marion car crash that killed 4 people, it took the fire department 2 hours of spraying water on it to extinguish the fire. It was reported to be a head on collision at speed. So the battery didn't directly cause the accident. The fire was an after effect. But, there's a lot of energy in those batteries!

Lithium Batteries – Does the Good Outweigh the Bad? – Long Island Boating World

liboatingworld.com

Last fall the president of ABYC issued a letter summarizing ABYC's attempts to have LFP batteries go into a thermal runaway, aka set fire. They failed to set fire to any of the batteries they tested. The conclusion and recommendation to the USCG was that LFP batteries are safe. Drop-in LFP batteries are only drop in by size, not by circuitry.

Here's a recent article from Ocean Navigator about the issue.

Lithium batttery safety - Ocean Navigator

The issue of lithium battery safety has gained importance as lithium batteries are increasingly used aboard voyaging boats. News stories of lithium batteries in electric cars and cell phones catching fire might convey the idea that these batteries are unreliable. Following a request from the US...

oceannavigator.com

 

[shemandr]

My sole intent in posting that article is to emphasize that a typical fire extinguisher is inadequate to put out a Li battery fire should it get started. I was moved to post this after reading @deminimis's post with the following quote "...and I should just make sure I have an additional fire extinguisher mounted near it..." I think that would be an inadequate response to this type of fire. Whether or not Li batteries are safe for boats is not a subject I'm qualified to comment on.
On this thread I've read about BMS dumps and other phenomenon that I have no understanding of. I can say there is a lot more I don't understand about these batteries than I do understand. They sound great but a fire on a boat you can't put out is a problem.

 

[deminimis]

Copy. Here's what I found on the subject (a few different sources). I thought they needed some super fancy dokicky. Seems not: "Class D fire extinguishers are effective against lithium-metal battery fires. Lithium-ion battery fires are Class B fires, indicating the presence of flammable liquids, so a standard dry chemical or ABC extinguisher can put them out."

 

[dlochner]

I've read about BMS dumps and other phenomenon that I have no understanding of

We all know, or should know, that turning a 1-2-both-off switch to off will fry the alternator. A BMS dump is basically the same problem, for what ever reason, the BMS stops accepting a charge current and there is no where for the current to go so the diodes fry. There are ways around this issue that are pretty simple. Balmar makes an Alternator Protection Module, having multiple batteries in parallel can also prevent this, having the BMS communicate with the alternator regulator that is is about to dump the load are some of them.

 

[deminimis]

On that point, my Suzuki is EFI. It does not actually require a battery to run. My assumption is the alternator provides the juice to the ecu, efi and whatever. If so, shutting off the battery while the outboard is running (either by switch or via the BMS) should not create a dump as the alternator is still supplying power to the engine components. Not much power, but it's something. Just wondering out loud. I'm going to have to try and run that down.

 

[Hayden Watson]

I have posted this before but it is good to repost it here. This is the from the spec sheet on my cells. As was stated in the Ocean Navigator article in post #48, ABYC tried and failed to get a LFP cell to burn even when they threw it into an already burning boat!
The Boating World article in post #44 makes no distinction between LFP and the other much more dangerous chemistries. All of the fires referenced were from batteries that were not LFP.
That is not to say that there is no fire danger from LFP, but it is not lithium fire. It is from the huge, short-circuit current capacity which will produce a lot of heat that can start combustibles in the area on fire. This type of fire is put out with normal methods such as water or CO2.

 

[Hayden Watson]

On that point, my Suzuki is EFI. It does not actually require a battery to run. My assumption is the alternator provides the juice to the ecu, efi and whatever. If so, shutting off the battery while the outboard is running (either by switch or via the BMS) should not create a dump as the alternator is still supplying power to the engine components. Not much power, but it's something. Just wondering out loud. I'm going to have to try and run that down.

I would not rely on the small bit of power that the engine electronics consume to protect the alternator. It is not power use that prevents diode boom. It is someplace for the current being produced to go that prevents it. Your tiny electronic curcuits cannot except the full output current of the alternators even for a mili-second. That current will cause a huge voltage spike in both the alternator diodes and also your ecu, efi and anything else in the engine. sounds very expensive.
For me, I have FLA batteries for start that cannot be disconnected from the alternator that are always ready to take the current until the regulator shuts down charging. SIMPLE, SAFE, EFFECTIVE.

 

[deminimis]

I'm running a powersport battery. This brand has been around for a while. They wouldn't be if they were killing the charging systems in motorcycles and PWCs. Thus, I have no concerns there. I was wondering about the possibility of switching the batt off while running, but not going to head down that path after further reflection.

 

[dlochner]

I'm running a powersport battery. This brand has been around for a while. They wouldn't be if they were killing the charging systems in motorcycles and PWCs. Thus, I have no concerns there. I was wondering about the possibility of switching the batt off while running, but not going to head down that path after further reflection.

The charging systems that use an alternator are different from the charging systems used on small motors, such as those on outboards, motorcycycles, and PWCs. The latter do not have an alternator and the current produced is much lower than that produced by even a small OEM alternator and is dependent on the motors RPM, while an alternator's current is a function of engine RPM and field current provided through the regulator.

The point here is comparing PWCs and Motorcycles electrical and charging systems to those powered by an alternator is not comparing apples to apples.

 

[jviss]

The point here is comparing PWCs and Motorcycles electrical and charging systems to those powered by an alternator is not comparing apples to apples.

Are you sure, Dave? I have been riding, repairing, and rebuilding motorcycles for 49 years and I can assure you that motorcycles have battery and charging systems essentially identical to cars - including alternators and voltage regulators. One minor difference from cars is that the rectifiers, i.e., the diodes, are usually outboard of the alternator, housed with the regulator. That's why you'll see big heat sinks on motorcycle voltage regulators.

 

[dlochner]

Are you sure, Dave? I have been riding, repairing, and rebuilding motorcycles for 49 years and I can assure you that motorcycles have battery and charging systems essentially identical to cars - including alternators and voltage regulators. One minor difference from cars is that the rectifiers, i.e., the diodes, are usually outboard of the alternator, housed with the regulator. That's why you'll see big heat sinks on motorcycle voltage regulators.

Commonly referred to as alternators most motorcycles do not have an alternator, they have stators. The difference is significant. The alternators we have on boats have a stator that spins inside a magnetic field, the current produced is controlled by varying the field current which increases or decreases the output current.

A stator works by spinning magnets inside of a fixed stator the current output is controlled not by controlling the magnetic field, rather by the speed at which the magnets are spinning. A stator needs to supply enough electricity to keep the motor running and lights on at idle speeds, a consequence of this is at higher speeds the voltage will increase with the unregulated output exceeding safe charging limits for the battery. To avoid over charging the battery the regulator can dump some current directly to ground to reduce voltage.

The regulators we have on our alternators do not have the ability to dump excess current to ground, thus in a BMS load dump there is no load and the current surges over heating the diodes in the rectifier. The motorcycle regulator provides a path to ground, thus if there is BMS load dump the excess current goes to ground, i.e., there is always a load on the stator. Both Balmar and Sterling sell devices which provide a path to ground on alternators to protect them in case of a BMS load dump or some other failure that would cause a current spike.

That being said, some larger cruising bikes may have alternators similar to the ones we have, in which case they too would be subject to the problems of a load dump.

Technical Article: How a Motorcycle Charging System Works - ElectroSpo

ELECTROSPORT presents a Technical Article explaining in detail how a motorcycle charging system works.

www.electrosport.com

 

[jviss]

You know, re-reading this thread there is a lot of bad information, and confusion. First, @tfox2069 has introduced some confusion by referring to a Victron battery monitor as a BMS, where that acronym, in the context of LiFePO4 (LFP) batteries, means something entirely different, the battery monitoring system for an array of LFP cells. Second, @shemandr has confused the danger of Li-Ion batteries, as used in older Teslas, with LiFePO4. (BTW, Tesla is going to LFP.). The former can ignite and are difficult to extinguish. The LFPs are much less likely to ignite - in fact, difficult to ignite. If they do ignite, a CO2 extinguisher will work to put out the fire.

I think the consensus is that LFPs are safe for boats, Li-Ion not so much.

As far as wrecking alternators and controlling charge levels in LFP banks, for example, wanting to leave them at 80% SOC for storage, I don't believe the BMS we want has been introduced yet. For the alternator diode problem you really need an output from the LFP BMS that will control the field current of the alternator, or perhaps just turn the regulator off, which would also drop the field current. Once the field current drops the alternator output current drops, and then disconnecting the load doesn't produce the voltage spike that can blow the diodes. Know that it's a V = L di/dt issue; in simple, Ohm's Law terms, if the current suddenly goes to zero, as happens when the load is disconnected, to satisfy Ohm's Law the Voltage must go to infinity, theoretically. In the real world, just very high, exceed the Vmax of the diodes. Then a BMS that would allow an all-LFP deployment and allow one to specify 80% or 100% SOC, and maybe even directly control a purpose-built regulator, or have an internal regulator for the alternator, is what one wants, I think.

 

[jviss]

Commonly referred to as alternators most motorcycles do not have an alternator, they have stators.

That's not so. A stator is just one part of an alternator, and won't do anything without a rotor. Most street bikes, and certainly the ones I've owned and worked on, mostly Hondas from the mid-sixties through eighties, and my 2001 BMW R1100RT, have stators and rotors, hence, alternators, along with rectifiers (diodes) and voltage regulators. Period.

in a BMS load dump there is no load and the current surges over heating the diodes in the rectifier.

That is not so. It is the voltage spike that kills the diodes, because the current goes to zero. See my post #59.

('Though it was many years ago, I did take the one-year "power" course as an electrical engineering undergraduate, which dealt with motors, generators, alternators, etc.).